The present invention relates to a method of determining the surface level of molten metal and to an apparatus therefor.
More particularly, the present invention relates to a method and apparatus which are suitably employed for determining the surface level of molten steel in the mold of continuous casting machine.
In the continuous casting method of steel, it is important to accurately measure the surface level of molten steel in a mold for controlling the teeming rate of molten steel from a tundish into the mold as well as for controlling the drawing speed of an ingot from the mold.
Varieties of measuring methods have hitherto been disclosed as the method of measuring the surface level of molten steel in a continuous casting mold. The representative examples include (1) the RI method, (2) the thermocouple method, (3) the eddy-current method, (4) the optical measuring method, (5) the infrared-camera measuring method and (6) the electrode immersion method. These methods, however, suffer from various problems as follows, respectively:
(1) The RI method requires a control for the security of operators and thus this method is now being replaced by other methods.
(2) The thermocouple method is an indirect and spot-type measuring method, and therefore, it has a poor responsiveness and accuracy.
(3) The eddy-current method is more excellent in accuracy and responsiveness than other methods, but this method requires to dispose a sensor close to the surface of molten steel. Moreover, in case of carrying out electromagnetic stirring of steel in the mold, the method is affected adversely by the generated magnetic field.
(4), (5) The optical measuring method and the infrared-camera measuring method are affected by fluctuations in thickness of the powder layer when powder is added onto the molten steel surface as a molten steel oxidation inhibitor or a lubricant.
(6) The electrode immersion method is a contact-type measuring method. Therefore, it may have interference with other equipment as well as is poor in operability.